Quote Originally Posted by kc261 View Post
Thank you for trying to explain this, but I'm still not sure what the difference is.

You give 2 examples of incomplete dominance which end up sounding basically like mixing paint together. Dark blue, no blue, or light blue in a het. Red, white (I assume?), or pink in a het.

Can you give an example of what co-dominance would be? I very vaguely remember something from junior high biology about roan cattle being a mix of red & white hairs. Would that be co-dom? Instead of each hair being pink? Which would be incomplete dominance?
My explanation sucked, for starters it wasn't complete, and secondly I actually reversed the definitions of the two. Let's hit this from another stand point. Let's say I breed an all black ball python to an all white ball python (let's assume for the moment, both of these traits are base mutations and neither are recessive).

If the alleles are co-dominant, the resulting ball python would be gray. This is the mixing of paint example that you gave. The proteins being produced by both alleles (in this case, pigment proteins) can only produce at about 50% the rate they should, so you have a total of 100% of the protein being produced.

If the alleles are incomplete dominant, the animal would be black and white. This is because each of the alleles is producing 100% of the protein. So the phenotype is a combination of the two.

The roan cattle is an example of co-dominance (but, just to add confusion to the mix, a roan horse is dominant).

In that case, is pastel technically incomplete dominance? Going back to the mixing paint idea, it is a little like someone mixed normal BP paint with the bright paint of a super pastel, and you end up with snakes with brighter color but not as bright as the supers. And if it were a true co-dom trait, we'd have spots that look normal and spots that look super pastel on a het version?
I can see why you would get to that point, because my explanation was really screwed up. But when the "paints mix" is co-dominant, when the paints are both displayed in the phenotype, but never mix, it's incomplete dominance.

I know lots of the "het for white" morphs have lots of flames. So I guess this might be a true co-dom, with spots of white showing through? And if they were incomplete dominant traits, you'd end up with snakes that ended up looking pale or washed out evenly across the whole snake in the het version, possibly looking something like a hypo?
Well, you are on the right track (had I not reversed the definitions in the first place you'd be dead right). The amount of the two incomplete dominant traits that show through is variable (and depends much more on environment than genetics).

Think of it as buckets of paint. Every ball python requires two gallons of paint to give a phenotype. If it's co-dominant, we mix the paints together really well and we have our phenotype. In incomplete dominance, we keep the paint seperate, but it's still only two gallons.